Key to Fort Dix terror case: Shadowy informer

He boasted of military experience and contacts with an illegal arms dealer.

He had previously worked as an undercover operative but once got in trouble for lying to the FBI. He endeared himself to one suspect but made another so nervous the man called police.

And month after month, he kept his recorder running -- and was paid for it.

In the hours after FBI agents arrested a band of South Jersey men for allegedly plotting to attack Fort Dix, officials were quick to anoint as their hero an unnamed store clerk who alerted police after seeing a video of the men training with weapons.

But the case almost surely owes as large a debt to another mystery man -- the paid informant who befriended the alleged conspirators, secretly taped the most incriminating statements and is likely to be a key witness against them.

U.S. Attorney Christopher Christie and the FBI declined to identify or discuss the man -- described in the criminal complaint only as Cooperating Witness 1 -- or a second cooperator in the probe. But new details about the defendants and a closer examination of court filings offer a clearer picture of "CW-1" and how he helped build the case against six alleged homegrown terrorists.

Prosecutors acknowledged the informant lived in the Cherry Hill apartment complex where agents arrested two suspects Monday night. Residents and a relative of one defendant said yesterday the description matches a man they knew as Mahmood, who lived with his wife and baby on the sixth floor of Hampshire Houses, then suddenly disappeared.

A brown-skinned man in his 40s, Mahmood restored cars in the parking lot, smoked in the hallways and was often on his cell phone but said little, his neighbors said. One said Mahmood recently told him he planned to move out.

"I did not feel good about him," said another resident, Sung Hwang. "He looked like he had something to hide."

There was no indication Mahmood was home when agents nabbed brothers Dritan and Shain Duka of Cherry Hill as they arrived to allegedly buy assault rifles from him. Four others were also arrested, charged with conspiring to kill U.S. soldiers or obtain illegal weapons. Prosecutors say the men -- foreign-born Muslims from Jordan, Turkey and the former Yugoslavia -- had no ties to known terror groups but were "radical Islamists" inspired by Osama bin Laden.

The undercover informant joined the case in March 2006, when he became friendly with 21-year-old Mohamad Ibrahim Shnewer.

Shnewer's mother, Faten, yesterday recalled that an older man named Mahmood had met her son at the family's grocery store in Pennsauken, took him to mosque services and once visited their home.

"He was not a friend of my son," she said, adding that if he is the informant, "he is a liar."

The cooperator's credibility will inevitably face more scrutiny. According to the complaint, CW-1 once got in trouble for lying to the FBI to protect a friend. Yesterday, attorneys in the Fort Dix case were eager to learn more.

"There's always holes in a case," said Troy Archie, attorney for a third Duka brother in the case, Eljvir. "You've just got to find out where they are and attack them."

CRITICAL RESOURCE

Informants are an important but controversial tool for law enforcement, sometimes carrying baggage such as criminal records or questionable motives. They have become critical as U.S. investigators strive to infiltrate and disrupt terror plots.

"It's become more prevalent because the mandate to prevent another attack leads the government to use informants more extensively and more aggressively than in the past," said Georgetown University Law School professor David Cole, who writes and lectures on terrorism.

In many of the cases, prosecutors have gambled that jurors would tolerate unsavory informants if it potentially meant saving lives.

In Portland, Ore., prosecutors used a small-time criminal to help nab seven suspects. Jurors in Brooklyn returned a guilty verdict after the government's key informant set himself on fire outside the White House. And in Newark, jurors rejected the argument by arms broker Hemant Lakhani that he had been illegally lured by an informant, who pressed Lakhani to find missiles, and undercover agents posing as dealers willing to sell them.

"Since 9/11, the entrapment defense is practically useless, because once a jury hears that a defendant is willing -- if not ready and able -- to commit an act of terrorism, the jury's heard enough," said Lakhani's attorney, Henry Klingeman.

In the Fort Dix case, Christie's office and the FBI have hours of tape to offer. According to the 25-page criminal complaint, the most inflammatory conversations -- about killing hundreds of soldiers -- occurred when the informant was alone with Shnewer. Fort Dix wasn't mentioned until August, when Shnewer suggested the two men scout targets. Shnewer also wondered whether the cooperator could lead the group, since he claimed to have military experience in Egypt.

During a meeting the next month, Shnewer explained to Shain Duka that he and his new friend had hatched a plan. "We've been brainstorming. . . . We got one, one idea for something and we want to know who is in."

Duka was slow to commit. "God willing, we will see," he said.

'I'M IN'Another suspect, Serdar Tatar, was equally cautious with CW-1. After the cooperator railed against the United States in a conversation last October, Tatar allegedly offered to steal a map of Fort Dix from the Italian restaurant his father operated in Cookstown.

Tatar then stalled for about a month, worrying about getting caught and deported. "I'm in -- honestly, I'm in," he allegedly told the informant in a taped conversation in November.

Three days later, Tatar called a Philadelphia police officer, saying he was being pressured to get a map for a plot that might be terrorist-related. But he later denied the plot and ultimately delivered the map.

Richard Sparaco, attorney for Serdar Tatar, wondered how much the informant nurtured the plot. "I'm going to be looking into whether the confidential informant may have crossed the line into confidential protagonist," Sparaco said yesterday.

According to the complaint, none of the Duka brothers or the sixth defendant, Agron Abdullahu, specifically discussed an attack on Fort Dix with either informant. Among them they had four guns, but the cooperator offered to get more from a source in Egypt.

In February, Eljvir and Dritan Duka allegedly told one of the informants they had trained with firearms because they wanted to participate in a "jihad," or holy war, overseas. A month later, Dritan and Shain Duka said they could launch such an attack in the United States; in the same conversation Shain Duka discussed joining the U.S. Army.